The present invention relates to a spindle unit for machine tools that facilitates switching of the rotation speed of the spindle unit. The present invention also relates to a method for operating a spindle unit of this type.
Spindle units are employed, for example, in motor-driven milling machines. A motor-driven milling spindle can be made as a single-piece or of separable components and typically includes an electric motor with a shrink-fit rotor. The rotor is supported between two bearings blocks. A tool tensioning system that typically includes a chucking head, a tie rod and a disk spring arrangement is arranged in the interior of the shaft. A tensioning system sensor located on the tie rod and a tool loosening rod are typically also attached at the end of the spindle unit.
In particular applications of a motor-driven spindle, a greater torque may be necessary than can be supplied by the electric motor. For this purpose, a dual-stage planetary drive is typically connected between the electric motor and the spindle head. Advantageously, the drive unit can be decoupled from the spindle head or the anterior milling spindle. Advantageously, the gear can be used if required, or may not be used. However, it would be undesirable to require removal of the anterior spindle from the drive unit for increasing the rotation speed or torque of the spindle. In particular, since the tie rod for the tool chucking system on the side of the drive unit facing away from the tool would then also have to be removed. A motor-driven milling spindle of this type is known in the art.
A commonly used rotatable hollow processing spindle formed as one piece and supported in a housing is described in the German patent publication DE 199 37 447. A tie rod is arranged in the processing spindle for clamping and/or loosening a tool chuck. The tie rod can rotate and axially move with the processing spindle. The rotor of the driving electric motor is mounted on the hollow processing spindle.
It would therefore be desirable and advantageous to provide an improved spindle device for machine tools and a corresponding method for operating a spindle device, which obviates prior art shortcomings and facilitates adjustment of the torque and/or or the rotation speed of the spindle.